God might not be equivalent to Brahman (or Vishnu) because it can't be ascertained if the given God being worshipped is the supreme reality or some devata worthy of worship. There is a Buddhist Tantra Kaalchakra which doesn't equate Islamic God to be the ultimate reality or any of traditional devatas. It claims their God to be some inferior being from lower heaven which they would presume as God.
Therefore the statement
Abrahamics (Christians, Muslims, Jews, etc.) worship God.
is subjective & can't be ascertained if they are really worshipping any true devata or the ultimate reality. They don't have any concept of praana pratishtha also, so it further invites the possibility of them worshipping some other entity than the Brahman.
But having said that, I would like to throw light on a specific verse of Bhagwat Geeta,
BG 12.3-4: But those who worship the formless aspect of the Absolute Truth—the imperishable, the indefinable, the unmanifest, the all-pervading, the unthinkable, the unchanging, the eternal, and the immoveable—by restraining their senses and being even-minded everywhere, such persons, engaged in the welfare of all beings, also attain Me.
It shows that if someone is worshipping an entity with upaadhis like
the imperishable, the indefinable, the unmanifest, the all-pervading, the unthinkable, the unchanging, the eternal, and the immoveable, then they are likely to worship the same Brahman. (Almost all Islamic schools don't believe in omnipresence/all-pervading of Allah).
...being even-minded everywhere, such persons, engaged in the welfare of all beings...
even if they worship the same Brahman (or Vishnu) they must have understanding of dharma (welfare of all beings) attested by practice of yoga (by restraining their senses and
even-minded everywhere) to attain to Brahman (or Vishnu) as it's indicated by the excerpt in the aforementioned verse,